1. Field of the Invention
The present invention generally relates to methods and apparatuses for handling substrates in a processing system. Specifically, the present invention relates to methods and apparatuses for operating a substrate handling mechanism within a substrate processing system.
2. Background of the Related Art
Vacuum processing systems for processing 100 mm, 200 mm, 300 mm or other diameter substrates are generally known. Typically, such vacuum processing systems have a centralized transfer chamber mounted on a monolith platform. The transfer chamber is the center of activity for the movement of substrates being processed in the system. The substrates are introduced into the system through one or more load lock chambers mounted on the transfer chamber. One or more process chambers mount on the transfer chamber at slit valves through which substrates are passed by a substrate handler, or robot, pivotably mounted in the transfer chamber. The substrate handler transfers the substrates through the transfer chamber and between the various other chambers, including the process chambers and the load lock chambers, attached to the transfer chamber.
The substrate handler is rotatable, mounts in the middle of the transfer chamber and can access each of the process chambers and load lock chambers in order to transfer a substrate therebetween. A simplified illustration of a mechanism for a substrate handler to rotate, extend and retract its substrate blade 10 is shown in FIG. 1a. The substrate blade 10 attaches to two struts 12, 14. The struts 12, 14 attach to pivot arms 16, 18. The pivot arms 16, 18 rigidly attach to a lower magnet ring 20 and an upper magnet ring 22. The lower and upper magnet rings 20, 22 are supported on a motor assembly housing and are free to rotate back and forth. When both magnet arms 20, 22 rotate in the same direction, either clockwise or counterclockwise, then they cause the pivot arms 16, 18 to rotate the substrate blade 10 in the same direction. When the two magnet rings 20, 22 rotate in opposite directions, such as when the upper magnet ring 22 rotates counterclockwise as viewed from the top, and the lower magnet ring 20 rotates clockwise, then the pivot arms 16, 18 pivot together to cause the substrate blade 10 to extend outward, similar to the configuration shown in dashed lines in FIG. 3. The substrate blade 10 is retracted by reversing the rotation of the lower and upper magnet rings 20, 22. The mechanism for rotating the lower and upper magnet rings 20, 22 uses two motors to separately operate the two magnet rings 20, 22 .
FIG. 1b shows a prior motor assembly for activating the rotation of the upper and lower magnet rings 22, 20. Upper and lower motors 24, 26 combined with gear reduction assemblies 28, 30 mount to the top 32 and bottom 34 of a motor assembly housing. A roughly cylindrically-shaped sidewall 36 supports the top 32 and bottom 34 and separates the ambient pressure environment on the inside of the motor assembly housing from the vacuum environment of the transfer chamber. The upper and lower gear reduction assemblies 28, 30 attach to upper and lower magnet clamps 38, 40 through drive shafts 42, 44, respectively. The upper and lower magnet clamps 38, 40 support upper and lower magnet rings 46, 48. The upper and lower magnet rings 46, 48 are magnetically coupled through the cylindrical sidewall 36 to the upper and lower magnet rings 22, 20, respectively, on the outside of the motor assembly housing.
As the inner upper and lower magnet rings 46, 48 rotate under the force of their respective motors 24, 26, the outer upper and lower magnet rings 22, 20 likewise rotate. The two motors 24, 26 can rotate the inner and outer magnet ring pairs 46, 48, 22, 20 in the same axial direction or in opposing axial directions in order to rotate, extend or retract the substrate blade 10 as described above. The separation of the inner and outer portions of the substrate handler by way of the magnetic coupling through the motor assembly housing effectively prevents particles and contaminants from entering the vacuum of the transfer chamber and potentially damaging the substrates being transferred therethrough.
Another example of a prior art motor assembly for activating the rotation of the upper and lower magnet rings 22, 20 is shown in FIG. 1c. This assembly uses two motors 50, 52 to drive two coaxial rings 54, 56 which mount two inner magnet rings (not shown) in turn to drive the outer magnet rings 22, 20, similar to the assembly shown in FIG. 1b. The drive shaft 58 connects motor 50 to gear 60. The gear 60 engages and drives gear 62, which is connected to inner shaft 64. The inner shaft 64 connects to the upper ring 54. Likewise, the motor 52 connects to drive shaft 66, which connects to gear 68. The gear 68 engages gear 70, which connects to outer shaft 72. The outer shaft 72 is coaxial with the inner shaft 64 and connects to lower ring 56. With this construction, the motor 52 operates the lower ring 56, and the motor 50 operates the upper ring 54.
A problem with these motor assemblies is that the two motors must be very carefully synchronized in order to properly move the substrate blade 10. If the motors do not operate in precise coordination, then the substrate blade 10 may be angled to one side or may be caused to wobble as it moves. For example, FIG. 1d shows a substrate handler with its pivot arms 16, 18 in solid lines properly coordinated to move the substrate blade 10 in a desired direction. However, if the motor operating pivot arm 16', shown in dashed lines, has an error, then the pivot arm 16' will be rotated slightly out of coordination with the pivot arm 18, and the substrate blade 10' will be slightly rotated to the side as well as partially retracted. This improper movement of the substrate blade 10 can result in an imprecise or unpredictable handling of a substrate and can misalign or damage a substrate on the substrate blade 10.
Attempts to maintain synchronization of the motors have typically involved programming the controller to monitor the errors detected in the rotation of the motors and to send commands to the motors to correct or coordinate the errors to achieve synchronization. This method requires highly sensitive sensors that send positional data to the controller and high-speed data transferring and processing capability to return the appropriate correction. To achieve this synchronization, a very complex system, with many potential points of failure, is needed to control operation of the substrate handler. Thus, the cost of the substrate handler and the potential for a failure in the system are fairly high.
Another problem with the two-motor substrate handlers described above is that the two motors require significant space. Two motors on top and bottom require space for the motors both above and below the assembly. Two motors on one side of the assembly require twice as much space on that side to house the two motors. Because of the overall size and complexity of a vacuum processing system, it is desirable to provide a substrate handler that occupies as little space as possible.
Another problem with the two-motor substrate handlers is the simple fact that two motors cost twice as much as one motor. Each motor represents a significant portion of the total cost of a substrate handler.
A need, therefore, exists for a substrate handler for use in a vacuum processing system that operates with only one motor that is no larger than a typical motor used in a prior art multi-motor substrate handler, but that can provide the same functionality as the prior art substrate handler with a simplified means for synchronizing the movement of the parts of the substrate handler.